1. Field of the Invention
The present invention relates to an error control method to replace the conventional transport protocol which brings about a bottleneck phenomenon in a communication between computers mutually communicating by accessing a network in comparison with a performance of a network being super-high-speedified and a computing speed of a computer in multimedia computer communication and, in particular, to an error control method for guaranteeing a multiparty reliable data transmission in a transport protocol which supports a many-to-many communication model.
2. Information Disclosure Statement
A recent tendency of persisting the globalization of the world brings many areas in a state and states all over the world close to each other through communication and information processing. These requirements are not simply satisfied through conventional usual mail, telephone and faximile but require a variety of multimedia application services such as group wares which support a group joint work which facilitates a concurrent face-to-face dialogue through application services such as remote lecture, remote medical treatment and remote video conference, etc.
One approach for sharing an application service which persist high speed and diversification is to develop transport protocols for multiple users. However, most of them are 1:1 transport protocol modes which share a single user which supports participating users with only existing user-system interaction. As one of the efforts to solve such problem, the field of communication network and application service highlights the transport protocol as an important research area, and the high speed transport protocol appears to be a new research field for a multimedia application in different machines high speed networks. Existing OSI TP(Transport Protocol) 4 stack or TCP/IP is a protocol provided to transmit a general text data and has many disadvantages in that it is not appropriate to provide a real time communication required in multimedia environment and a communication to reliably process a lot of data. In addition, these protocols are not appropriate for a communication protocol which can satisfy requirements accompanying an increase in a variety of computer communication networks, an increase in transmission rate according to development of communication technology and transmission apparatus, a development of computer technology and an extension of new application service area including a varietymedia. Furthermore, since these protocols were developed in the time when the bandwidth of network was narrow, the network had high error occurrence rate and there was lack of system resources, the main object of the protocols was an efficient use of bandwidth and an efficient performance of error detection and recovery. However, to solve the performance degradation due to the structural problem of the existing protocol, the existing high speed communication environment uses a method of revising or extending the function of existing protocol and minimizing the protocol processing time and a method of designing a new protocol structured to be appropriate to the existing high speed network environment. Since the extension of existing protocol among the methods can not be a long term solution, a research on the design of new protocol is vigorously carried out.
The error control is to reliably provide the data transmission necessary for multimedia application such as collaborative work in inter-multi-user transport protocol environment of multimedia computer communication. Since the existing error control methods have been used mainly for document-oriented text data in the time when the network was unsafe due to jitter and delay, etc., and the performance such as speed was poor, they present too many disadvantages to be used as an error control method required in the super high speed information communication environment based on the existing multimedia and super high speed transmission network.
To guarantee the inter-multi-user reliable data transmission, the reliability of data packet transmission and of group membership of subscriber of communication must be guaranteed. To provide the reliability of this type, the problem of acknowledge implosion and scalability of group membership which does not occur in the protocol based on end-to-end or peer-to-peer communication such as Transmission Control Protocol (TCP) must be considered.
A real conference wants to have the guaranty of strict transmission delay service instead of reliable transmission service. On the other hand, the collaborative application such as common editor or distribution of medical image information absolutely requires the transmission service guaranteeing the reliability. Recently, reliable multicast transmission protocols of various types have been developed to accommodate the requirement of application program requiring the quaranty of reliability, and there are results of research which compares and analyses the protocols, however, such protocols have not efficiently solved the problem of salability of group size and reliability.
In the conventional end-to-end communication in which a transmitter and a receiver establish a 1:1 connection, after the receiver receives the data from the transmitter, the receiver acknowledges the state of the received data according to the method of reliably transmitting and receiving the data. The error control is the function of detecting and solving the errors occurring at the time of data transmission between the transmitters and receivers. The errors that can occur in the procedure of transmission and reception are deformation of packet content, change in the order of packet arrival, duplication of packet arrival and loss of packet, etc. These error control functions are three functions such as error detection, error reporting and error recovery (correction), and the following researches are carried out on them.
The error detection function is to check whether the packets arrive in the order of transmission without deformation of packet contents. The error detection has a procedure of receiving a message by using the information such as sequence number, packet length and data checksum, checking the messages and receiving next message.
The error reporting function is to transfer to the transmission side the informations about the arrival of wrong packet or the loss of packet, and for the error reporting function, a Negative Acknowledge (NACK) mode of selecting the packet to which the error occurred and acknowledging is well known rather than Acknowledge (ACK) mode of acknowledging whenever the packet arrives. In general, since the existing protocol does not have such error exporting function but frequently detects the error based on the arrival or not of packet by using a Positive Acknowledge (PACK) mode in which the receiver securely acknowledges to the transmitter within a predetermined period, if the existing protocol is applied to a many-to-many communication, it causes an overload at the time of data transmission.
The error recovery (correction) function is to recover a reported error by retransmitting the packet corresponding to the reported error. A method of retransmitting all packets after the packet to which the error occurred is used, and the method is easy to implement so that it can be easily applied to a communication network having high error rate, therefore, the method is adopted and used in the existing protocol, however, nowadays a revised method is required in the super high speed network environment in which the reliability of the network is improved and a great amount of data must be transmitted a short time period.
The functions described above is a method of controlling errors occurring in the end-to-end communication composed simply of one transmitter and one receiver and is not appropriate to solve the errors occurring concurrently and in a bundle between one or some transmitters and many receivers in the many-to-many multiple points, multiple user communication such as multimedia environment.